PROJECT SUMMARY/ABSTRACT Gait disturbances in older adults are common, costly, and contribute to loss of functional independence, more so in African Americans (AA) than whites. Yet the pathway to mobility decline is poorly understood and grossly understudied in AA. Prior studies suggest hypertension, cerebral small vessel disease (e.g., infarcts and white matter hyperintensities) and poor cognition may have substantial effects on gait and are more prevalent in AA. These factors are also associated with cerebral perfusion. Lower static cerebral perfusion in whites is associated with slower gait speed, and this relationship is modified by systolic blood pressure (SBP) and age. These relationships have not been examined in AA, and interrelations of late-life BP, cerebral perfusion and mobility have not been characterized. Thus, there is limited understanding of how these factors affect mobility. This study will collect measures of cerebral perfusion in a biracial sample in Jackson, Mississippi via 3T arterial spin labeled perfusion MRI and will compare findings to whites in a cohort in Minnesota. The combination of African American and white participants will enable us to further disentangle race- and geographic influences related to mobility decline. This study will cost-effectively define interrelations of historical and late-life BP levels, late-life cerebral perfusion and late-life mobility AA and whites at substantial cost savings via these three aims: Aim 1: Determine optimal SBP ranges in late life associated with better mobility and less mobility decline across age and cerebral perfusion levels. H1: Optimal BP ranges associated with better mobility and less decline in mobility will be lower in older adults with higher cerebral perfusion and will increase with lower cerebral perfusion levels and older age. Aim 2: Quantify relations of late-life BP, mid-life BP, and cumulative BP to late-life cerebral perfusion. H2: Higher mid-life BP and greater cumulative BP exposures will be more strongly associated with lower cerebral perfusion than late-life BP. Aim 3: Quantify racial differences in interrelations of late-life BP, cerebral perfusion and mobility/ mobility decline. H3.1: Cerebral perfusion will be lower in AA than in whites. H3.2: Among all participants with better cerebral perfusion, optimal BP ranges associated with better mobility and less mobility decline will be lower in AA than in whites. Findings will provide the first evidence base for testing and refining personalized medicine in BP management in relation to mobility and will elucidate contributors to mobility disparities in AA.